The proposed research will deal primarily with corticofugal, especially cortico-cortical, pathways from the striate cortex and with synaptic connections in the dorsal lateral geniculate nucleus in mammals. The objectives are: 1. To study specifically and comparatively the system of cortico-cortical connections from the striate cortex in different species. These will include species of the following orders: Rodentia (grey squirrel), Lagomorpha (rabbit), Carnivora (cat), and Primates (new world: owl monkey; old world: rhesus monkey). Three main objectives will be emphasized: a) the definition of cortical areas that receive direct inputs from the striate cortex, i.e., that perform further cortical processing of visual information; b) study of the topography of these connections, by use of double or triple label anatomical tracing methods; c) attempt at establishing homologies between these areas, based on connectivity patterns. 2. Identification of synaptic terminals in the dorsal lateral geniculate originating from fibers of the thalamic reticular nucleus, using EM autoradiography. 3. Study of effects of early postnatal eye enucleation upon central visual pathways in the rat, that may be induced by the abnormal ipsilateral retino-geniculate connection that is established.